A Mixed Basis Approach for the Efficient Calculation of Potential Energy Surfaces

First principles calculations based on density functional theory are having an incerasing impact on our understanding of molecule-surface interactions. For example, calculations of the multi-dimensional potential energy surface have provided considerable insight into th edynamics of dissociation processes. However, these calculations using a plane-wave basis set are very compute expensive if they are to be fully converged with respect to the plane-wave energy cutoff, k-point sampling, supercell size, slab thickness, etc. Because of this, in this study, we have implemented a mixed-basis set approach which uses pseudo-atomic orbitals and a few low-energy plane waves as the basis set within a density functional, pseudopotential calculation. We show that the method offers a computationally cheap but accurate alternative. The energy barrier for hydrogen dissociation on Cu(111) is calculated as an example.